In an interview with RT, a spokesman for the Kurdish YPG militia accused Turkey of providing a clear transit route for the chemical weapons that were deployed against them near the city of Aleppo on Tuesday.

Syrian anti-government militants “took advantage of the ceasefire” to launch attacks against a Kurdish-controlled area near Aleppo in northern Syria, Redur Xelil told RT. The attackers targeted a civilian district of what was once Syria’s biggest city, and has since become a key battleground. According to Xelil, the shells emitted an “unnatural smell” and “yellow smoke” upon impact, indicating that chemical weapons were involved.

“Our sources inside the rebel groups have confirmed that toxic substances were used. We also have verified information that sarin gas was delivered to them from Turkey. All signs point to the fact that these factions were using banned weapons, but we cannot access the launching area, as it is located on the front between the Turkish and rebel forces,” Xelil told RT by Skype from Rojava in Syria.

Kurdish deputies in the Turkish parliament have previously accused Ankara of supplying Islamic State (IS, formerly ISIS/ISIL) and other jihadist groups inside Syria with chemical weapons, which are used both in their fight against the Syrian government and to pin responsibility for their deployment on the regime of President Bashar Assad.

Tuesday’s attack, which also involved phosphorus, did not result in any severe casualties.

“This attack was a failure, but this doesn’t mean that there won’t be another one. We are convinced the enemy has improvised shells containing phosphorus and sarin gas,” said Xelil.

Last month, the Organization for the Prohibition of Chemical Weapons (OPCW) accused IS of using chemical weapons against Kurdish forces throughout 2015. Reports emerged on Wednesday revealing that the jihadist group had launched a new chemical attack on the Kurdish village of Zaza in northern Iraq, in which more than 40 civilians suffered chemical burns and lung damage.